Many kinds of removable band-type couplings for pipes exist in the art. It is noted that throughout the specification and claims, the term “pipe” encompasses any kind of generally cylindrical object, and the terms “clamp” and “coupling” are used interchangeably.
Pipeline leakage must be prevented for both economic and environmental reasons, depending on the nature of the fluid being transported. When needed repairs are inevitably carried out under field conditions, and in many situations there is a requirement that the flow of fluid in the pipeline may not be interrupted for any reason. Thus replacement of a faulty pipe joint is not an option.
Prior art seals are not capable of being used externally over an existing coupling or existing bell joint. Prior art seals lack the internal space needed if the repair seal is to be applied over and around an existing but leaking pipe joint. A further problem with many prior-art seals arises when the fluid being transported is under high pressure. This results in the seal lips being gradually pushed outwards, eventually leading to complete seal failure.
A solution to the above problems is described in Israel Patent 196511, assigned to Krausz Industries Ltd. This patent describes an external seal completely enveloping the existing leaking seal. This is referred to as a capsulation assembly. The capsulation seal assembly fits over existing bell-shaped joints, sleeve joints and the like, and seals the joint. The assembly is briefly described with reference to FIGS. 1-5.
FIG. 1 illustrates an existing bell joint coupling 1 that couples two pipes 2 and 3. A capsulation assembly 4 includes a seal 5 with an internal cavity 6 that is sized to fit over the bell joint 1, without having to disturb the bell joint 1. The seal 5 is tightened by clamp members 7 (with tightening fasteners, not shown).
FIG. 2 illustrates an existing sleeve joint coupling 8 after repair by capsulation assembly 4. As before, internal cavity 6 is sized to fit over the sleeve joint 8.
FIG. 3 illustrates the profile of seal 5, which has an outer substantially rectangular shape with surfaces 5A and internal cavity 6. Spaced-apart, circumferential passageways 9 are each formed through a portion of a seal lip 10. Axial passageways 11, transverse to circumferential passageways 9, are formed in seal lips 10 and form a hydraulic connection between circumferential passageways 9 and internal cavity 6. The hydraulic pressure within internal cavity 6 applies additional hydraulic pressure on seal lips 10 by means of fluid flowing through the passageways and pressing the lip 10 further against a pipe (not shown).
Seal lips 10 have seal surfaces 12 formed with ridges 13, which contact the pipes 2 and 3 in FIGS. 1 and 2. The ridges 13 provide clearance for surface irregularities and for small solid particles which may be entrained in the fluid flowing through the pipes.
In FIG. 4, the seal 5 is formed with surfaces 14 and 15 that slope inwards from bottom surface 16. In FIG. 5, an additional circumferential passageway 17 is formed through a portion of seal lip 10.
However, a problem of the prior art assembly can occur after tightening clamp 7. The tightening applies pressure to seal 5 and can cause portions of seal 5 to escape or migrate partly out of the clamp.